1. Field of the Invention
The present invention relates to a multi-band antenna, more particularly to an antenna with peak gain suppression and a relatively high radiation efficiency.
2. Description of the Related Art
Referring to FIG. 1, a conventional dual resonance inverted-F antenna 9 includes a linear first radiator portion 92, a linear second radiator portion 93, a grounding portion 95, and a step-like connecting portion 94 connecting electrically the first and second radiator portions 92, 93 to the grounding portion 95. The first radiator portion 92 and the connecting portion 94 constitute a first radiator arm resonant in a first frequency band. The second radiator portion 93 and the connecting portion 94 constitute a second radiator arm resonant in a second frequency band that is lower than the first frequency band.
The antenna 9 is applicable to portable devices, such as portable computers, and is adapted for operation in Wireless Local Area Networks (WLAN) and Worldwide Interoperability for Microwave Access (WIMAX) networks. To reduce interference from the antenna 9, gain of the antenna 9 is generally limited by decreasing the height, increasing the Voltage Standing Wave Ratio (VSWR), or shifting the operational frequency bands. However, the above-mentioned schemes compromise radiation efficiency of the antenna 9.